Reactions of Hydridoirida-β-diketones with Amines or with 2-Aminopyridines: Formation of Hydridoirida-β-ketoimines, PCN Terdentate Ligands, and Acyl Decarbonylation

The hydridoirida-β-diketone [IrHCl­{(PPh2(o-C6H4CO))2H}]
(1) reacts with benzylamine (C6H5CH2NH2) to give the hydridoirida-β-ketoimine
[IrHCl­{(PPh2(o-C6H4CO))­(PPh2(o-C6H4CNCH2C6H5))­H}] (2),
stabilized by an
intramolecular hydrogen bond. 2 reacts with water to
undergo hydrolysis and amine coordination giving hydridodiacylamino
[IrH­(PPh2(o-C6H4CO))2(C6H5CH2NH2)] (3). Cyclohexylamine or dimethylamine lead to hydridodiacylamino
[IrH­(PPh2(o-C6H4CO))2L] (4–5). In chlorinated
solvents hydridodiacylamino complexes undergo exchange of hydride
by chloride to afford [IrCl­(PPh2(o-C6H4CO))2L] (6–9). The reaction of 1 with hydrazine (H2NNH2) gives hydridoirida-β-ketoimine [IrHCl­{(PPh2(o-C6H4CO))­(PPh2(o-C6H4CNNH2))­H}] (10), fluxional in solution with values for ΔH⧧ of 2.5 ± 0.3 kcal mol–1 and for ΔS⧧ of −32.9
± 3 eu. A hydrolysis/imination sequence can be responsible for
fluxionality. 2-Aminopyridines (RHNC5H3R′N)
react with 1 to afford cis-[IrCl­(PPh2(o-C6H4CO))­(PPh2(o-C6H4CHNRC5H3R′N))] (R = R′ = H (11),
R = CH3, R′ = H (12), R = H, R′
= CH3 (13)) containing new terdentate PCN
ligands in a facial disposition and cis phosphorus atoms as kinetic
products. The formation of 11–13 requires
imination of the hydroxycarbene moiety of 1, coordination
of the nitrogen atom of pyridine to iridium, and iridium to carbon
hydrogen transfer. In refluxing methanol, complexes 11–13 isomerize to afford the thermodynamic products 14–16 with trans phosphorus atoms. Chloride
abstraction from complexes [IrCl­(PPh2(o-C6H4CO))­(PPh2(o-C6H4CHNRC5H4N))] (R
= H or CH3) leads to decarbonylation of the acylphosphine
chelating group to afford cationic complexes [Ir­(CO)­(PPh2(o-C6H4))­(PPh2(o-C6H4CHNRC5H4N))]­A, 17 (R = H, A = ClO4) and 18 (R = CH3, A = BF4) as a cis/trans = 4:1 mixture
of isomers. Single crystal X-ray diffraction analysis was performed
on 6, 9, 13, and 14.